The question remains: Is diet soda bad for you? Here are the pros and cons of these fizzy drinks.

The Pros and Cons of Drinking Diet Soda

Pro #1 - Aspartame is Not Carcinogenic

One of the key ingredients in diet soda is aspartame. It is common to see reports in the media linking this with health problems.

A 2013 Channel 5 (UK) documentary named "50 Shocking Facts about Diet and Exercise" claimed that aspartame is carcinogenic [potentially cancer-causing] and manufactured in the same factories that made napalm for the Vietnam War. A cause for concern, maybe? Not quite.

"The scientific consensus following several systematic reviews of hundreds of publications is that for the general population, aspartame is safe."

The belief that aspartame is carcinogenic is not reinforced by evidence. The seal goes on to say:

"The reports linking aspartame to cancer development in studies with rats and other so-called detrimental effects have not been confirmed in a large number of studies in people, nor in epidemiological studies [of how and why diseases occur]."

Pro #2 - A Cheeseburger Contains 9 Times More Phenylalanine Than a Diet Soda

There are certain people who should avoid aspartame where possible, but this is a very limited figure. These people are sufferers of phenylketonuria, a rare genetic disorder. When sufferers of this condition metabolize aspartame, it produces phenylalanine which they have to avoid in their diet.

This is such a rare illness, however, that only 1 in 10,000 people will be affected. For the vast majority, this poses no problem.

There is 9 times the amount of phenylalanine in a cheeseburger as there is in a 330ml can of diet soda so if you are really concerned about limiting your intake, you might want to drop the fast food first.

Pro #3 - Fruit Juice Contains Far More Methanol

Another compound produced when ingesting aspartame is free methanol. This has caused some alarm, but the reaction is not justified. 330ml of fruit juice contains double the methanol contained in a can of diet soda, so no point in panicking.

It is suggested that as little as 10ml of methanol could potentially make you go blind by damaging the optic nerve but for this to occur, you would have to drink 500 cans of diet soda straight. If you did want to test this out, the guy waiting behind you in the supermarket queue would probably kill you before the drink could.

Pro #4 - Diet Soda Doesn't Cause Weight Gain

Trying to get in shape and wondering whether it is still worth dropping the diet soda? Don't stress. There are no studies which show sugar-free soda to be a direct cause of weight gain.

Quite the opposite, in fact.

The University of North Carolina found that substituting caloric drinks for diet soda [and water] resulted in noticeable weight loss. Similarly, a study conducted by Johns Hopkins Bloomberg School of Public Health showed that reducing your intake of zero-calorie soda did not specifically aid weight loss.

While sugar-free soft drinks are safe, they don't actually provide your body with much in the way of nutrition.

Con #1 - Diet Soda Acidity May Cause Dental Erosion

It is worth realizing that diet soda drinks are not without their issues. No sugar, no problems? Not exactly.

Professor Chris Seal, Lecturer in Human Nutrition at Newcastle University, states that diet soda is still very acidic and can cause problems due to dental erosion. Professor Seal adds,

"Fizzy drinks may be better in that they have zero calories and zero sugar, but they also contain additives which may cause problems for some people."

Best way to get around this? Limit your consumption, and drink in moderation.

Con #2 - Diet Soda Lacks Any Real Nutrition

While sugar-free soft drinks are safe, they don't actually provide your body with much in the way of nutrition. Professor Seal states that aspartame is,

"To all intents and purposes, of no use to the human body, all it does is stimulate the sweet receptors on the tongue."

Seal also explains how,

"In theory, phenylalanine could be used in the body as a component of protein, but the amount typically consumed is so small this would not be of significance to the normal human body."

If you are looking for something nutritious to aid your health, you will not get a lot from diet soda drinks but that does not mean they are unhealthy. They are fine to consume in moderation, and do not pose much of a health risk.

Con #3 - There May Be a Correlation Between Diet Soda and Weight

Again despite there being no evidence that diet soda causes weight gain [see the last pro point] - some studies, including the National Health and Nutrition Examination Survey (NHANES), have shown a correlation between diet soda consumption and weight gain in adults.

"This is so surprising," says Marilyn Townsend, Nutrition Specialist at University of California Davis, "because we expect these low-calorie sugar substitutes to assist with weight loss."

These results can be explained in two main ways. Firstly, the sweeteners used in diet soda may stimulate the sweet-taste receptors in the mouth which could lead to overeating. Secondly, people who drink a lot of zero-calorie soda may effectively reward themselves by underestimating how many calories they are consuming elsewhere.

Correlation and causation are two different things. Diet soda does not appear to cause weight gain, so using in moderation alongside exercise and an otherwise healthy diet would be fine.

Should You Drink Diet Soda?

Diet soda drinks with reduced sugar and calories are far safer than the sugary kinds. Artificial sweeteners normally included have not been seen to cause negative health problems such as weight gain, disease or impaired brain function. While moderate use seems to be fine, in excess your teeth may suffer. If you are looking for something to boost your brain power or help your heart, you may want to continue the search. However, the odd glass of sugar-free soda alongside sound training and nutrition is not a recipe for disaster.